1. Field of the Invention
This invention relates to a cutter holder device in a pelletizer, and more particularly to a novel improvement thereof that a cutter shaft is coupled to a cutter holder through a crowned involute spline gear and an elastic member so that cutter blades are held completely in contact with a die even when the pelletizer is continuously operated at a temperature condition characterized by high temperature, variation of temperature during operation and extended operation.
2. Description of the Prior Art
There are a variety of cutter holder devices of this type. A typical one of the cutter holder devices, which is popularly employed, is as shown in FIG. 2.
In FIG. 2, reference numeral 1 designates a cutter shaft. A cutter holder 3 substantially T-shaped in section is coupled to the cutter shaft 1 through a key 10.
A support member 5 is secured to the front end face 1a of the cutter shaft 1 with a bolt 4. The cutter holder 3 is positioned by means of the support member 5. More specifically, the rear end face 3a of the cutter holder 3 is abutted against the shoulder 1b of the cutter shaft 1 with the support member 5.
The cutter holder 3 has a mounting peripheral portion 3b, to which a plurality of cutter blades 6 are secured with mounting bolts 7. The cutter blades 6 are slidably rotated while being pushed against the die surface 8a of a die 8.
When the cutter blades 6 are slidably rotated on the die surface 8a through the cutter holder 3 by the cutter shaft 1, a molten resin discharged from the die 8 is cut into pellets by the cutter blades 6.
The conventional cutter holder device designed as described above suffers from the following difficulties:
In general, in order to obtain pellets satisfactory and uniform in configuration, the squareness between the cutter shaft and the die surface must be considerably high in accuracy. For this purpose, the cutter shaft is joined with the cutter holder by fitting the former into the latter with no play therebetween, and the key is used to transmit torque from the cutter shaft to the cutter holder. On the other hand, the pelletizer is operated at the temperature condition specified by high temperature and, variation of temperature during operation, and therefore the cutter shaft may be adversely affected in balance by thermal expansion, or when the pelletizer is operated for a long period of time, the support member supporting the cutter shaft may be worn out, the squareness between the cutter shaft and the die surface is lowered; that is, a portion which is not brought into contact with the cutter blades is partially developed on the die surface on which the cutter blades are slidably moved. As a result, the conditions of cutting the molten resin discharged from the die are variable, which makes it considerably difficult to obtain pellets satisfactory and uniform in configuration.